1. Field of the Invention
The present invention relates to a tubular electric double-layer capacitor, and particularly, to a tubular electric double-layer capacitor, comprising an electrode roll made by rolling a superposed assembly including a band-shaped positive pole and a band-shaped negative pole superposed on each other with a first separator interposed therebetween and a second separator superposed on one of the band-shaped positive and negative poles, so that the second separator is located on an outermost side, and a vessel in which the electrode roll is accommodated.
2. Description of the Related Art
In a conventional electrode roll, a portion of one of the band-shaped positive and negative poles located on an outermost periphery, namely an annular outer peripheral surface of a last turn, has no mating electrode opposed thereto.
In the prior art, there is a disadvantage that the annular outer peripheral surface of the last turn does not participate in ensuring an electrostatic capacity and hence, is useless. The amounts of band-shaped positive and negative poles utilized are different from each other, thereby bringing about an unbalance between potentials, and causing deterioration of the performance.
It is an object of the present invention to provide a tubular electric double-layer capacitor of the above-described type, wherein the entire opposite sides of the band-shaped positive and negative poles of the electrode roll can be utilized effectively for ensuring an electrostatic capacity, and deterioration of the performance can be inhibited to the utmost by equalizing the amounts of band-shaped positive and negative poles utilized.
To achieve the above object, according to the present invention, there is provided a tubular electric double-layer capacitor comprising an electrode roll made by spirally rolling a superposed assembly including a band-shaped positive pole and a band-shaped negative pole superposed on each other with a first separator interposed therebetween and a second separator superposed on one of the band-shaped positive and negative poles so that the second separator is located on an outermost side, and a vessel in which the electrode roll is accommodated. A tubular electrode is mounted on the electrode roll to come into contact with an outer peripheral surface of the electrode roll, and the polarity of the tubular electrode is set to be opposite from that of a portion of the one of the band-shaped positive and negative poles which is located on an outermost periphery of the electrode roll.
With the above arrangement, the annular outer peripheral surface of the last turn, which is a portion of one of the band-shaped positive and negative poles of the electrode roll, is opposed to the tubular electrode having a polarity different from the polarity thereof with the second separator interposed therebetween to the mating electrode. Thus, it is possible to effectively utilize the entire opposite sides of the band-shaped positive and negative poles of the electrode roll for ensuring an electrostatic capacity, thereby increasing the electrostatic capacity more than that in the prior art. In addition, the potentials of both the poles can be balanced with each other by equalizing the amounts of band-shaped positive and negative poles utilized, thereby inhibiting the deterioration of the electric double-layer capacitor to the utmost.